1. Field of the Invention
This invention relates to a vertical type forming, filling and closing machine for filling an object substance in the form of a liquid or paste into a bag and sealing the bag to package the object substance.
2. Description of the Related Art
Various vertical type forming, filling and closing machines for a flexible package are already known. A filling section of an exemplary conventional vertical type forming, filling and closing machines for a flexible package is shown in FIGS. 1 and 2a which are side and front elevational views, respectively, of such a filling section and also in FIG. 2b which is a sectional view taken along line A--A of FIG. 2a.
Referring to FIGS. 1, 2a and 2b, the filling section of the conventional vertical type forming, filling and closing machine for a flexible package is constructed to fill object substance A injected from injection nozzle 902 into a flexible bag and to close the flexible bag.
Injection nozzle 902 for injecting object substance A therethrough is fitted in injection pipe 911, and bag forming guide 913 for forming sheet film 925 into a tubular shape is mounted on the outer periphery at the substantially mid portion of injection pipe 911. Tubular film 901 formed into a tubular shape by bag forming guide 913 is then heat sealed along contacting surfaces along the opposite edges thereof by vertical sealing section 922 provided below bag forming guide 913.
A pair of film feeding rollers 923.sub.1 and 923.sub.2 each composed of two disk-shaped rollers disposed such that tubular film 901 is held between the four rollers, a pair of cylindrical stripping rollers 924.sub.1 and 924.sub.2 for stripping the object substance A injected into tubular film 901 and a pair of horizontal sealing blades 920.sub.1 and 920.sub.2 for sealing the empty filling portion of tubular film 901 obtained by stripping rollers 924.sub.1 and 924.sub.2 are provided in an individually opposing relationship to each other on the opposite sides of tubular film 901 below injection pipe 911. Stripping rollers 924.sub.1 and 924.sub.2 are constructed for individual movement in a direction perpendicular to the direction of movement of tubular film 901, that is, in a leftward and rightward direction in FIG. 1, in order to move down tubular film 901, into which object substance A has been injected.
Cutting blade 921 for cutting the empty filling portion of tubular film 901 is provided substantially at the mid portion of horizontal blade 920.sub.1. Guide stretching member 926 having two pins extending outwardly downward is mounted at the lower end of injection pipe 911.
In the conventional vertical type forming, filling and closing machine for a flexible package having the construction described above, sheet film 925 is shaped into tubular film 901 by bag forming guide 913 and vertical sealing section 922, and as a motor (not shown) for driving the film feeding rollers 923.sub.1 and 923.sub.2 rotates, tubular film 901 is drawn out downwardly while it is put into an open condition by guide stretching member 926. Object substance A is injected when stripping rollers 924.sub.1 and 924.sub.2 and horizontal sealing blades 920.sub.1 and 920.sub.2 are held spaced away from each other after rotation of film feeding rollers 923.sub.1 and 923.sub.2 is stopped. After completion of this injection, striping rollers 924.sub.1 and 924.sub.2 are moved toward each other to hold tubular film 901 therebetween and then rotated in the directions indicated by each of the arrow marks in FIG. 1 together with film feeding rollers 923.sub.1 and 923.sub.2. As a result of this rotation of stripping rollers 924.sub.1 and 924.sub.2, tubular film 902 is drawn down, and the empty filling portion of tubular film 901 is formed by stripping rollers 924.sub.1 and 924.sub.2. When tubular film 901 is drawn down to the position shown in FIGS. 1 and 2a by rotation of rollers 923.sub.1, 923.sub.2, 924.sub.1 and 924.sub.2, horizontal sealing blades 920.sub.1 and 920.sub.2 are advanced toward each other to a position at which they hold the tubular film 901 therebetween and perform sealing of tubular film 902, after which tubular film 902 is cut by cutting blade 921. Thereafter, stripping rollers 924.sub.1 and 924.sub.2 and horizontal sealing blades 920.sub.1 and 920.sub.2 are spaced away from each other to allow the sequence of operations described above to be repeated.
Conventionally, injection of a fixed amount of an object substance into a bag is realized by injection of such object substance to a predetermined height from the bottom of the bag.
In the conventional vertical type forming, filling and closing machine described above, since the object substance is injected into a bag through an object substance injection nozzle provided at a predetermined height from the bottom of the bag, air is often contained in the bag. Consequently, the amount of the object substance injected into the bag to a predetermined height from the bottom of the bag may not be fixed. Accordingly, significant errors in the packaging amount may be a problem.
Further, while a fixed amount of the object substance to be injected into a tubular film is achieved, in the conventional vertical type forming, filling and closing machine for a flexible package described above, by limiting injection of the object substance to a predetermined height, the object substance injected into the tubular film will spread along the inner wall of the tubular film and the weight of the thus spread object substance will be applied to the inner wall of the tubular film to cause some deformation of the tubular film. In case this deformation occurs on the tubular film, even if the height of the object substance to be packed into the tubular film is limited to a predetermined height, the packaging amount will not be fixed. Accordingly, the amount of object substance to be packaged will not be fixed, and significant errors in the packaging amount may be a problem.
While it seems a possible solution to inject the object substance by a predetermined amount in every injecting operation in order to cope with the problems described above, the solution still has a problem in that, when this construction is employed, if air is contained in the bag, the volume of the bag increases so as to cause deformation of the bag, and accordingly, bags thus produced will not be standard in shape.